Tropical Storm Isaac soaks saturated Gulf Coast

NEW ORLEANS--Tropical Storm Isaac dumped more rain onto an already saturated Gulf Coast on Thursday as residents sought safety from flooding and officials warned of tornadoes and life-threatening storm surges.

The National Hurricane Center said the slow-moving mass of fierce weather, which was downgraded from a hurricane to a tropical storm Wednesday, would weaken and move north but continue to produce heavy rain for two days.

At 1200 GMT, Isaac was located about 125 miles (205 kilometers) northwest of New Orleans, where officials on Wednesday ordered the evacuation of some 3,000 people in coastal Plaquemines Parish, the area hardest hit by the storm.

The storm has revived memories of Hurricane Katrina, which devastated the region exactly seven years ago, flooding New Orleans and killing at least 1,800 people in the broader Gulf Coast area.

This time around, new multibillion-dollar post-Katrina flood defenses appeared to be holding but authorities still urged residents to stay indoors.

The city's airports and the Gulfport-Biloxi International airport in Mississippi remained shuttered.

Packing maximum sustained winds of 45 miles (75 kilometers per hour), the storm could dump up to 14 inches (35 centimeters) of rain over much of Louisiana, Mississippi, southwest Alabama and Arkansas through Friday.

Some areas could see levels of up to 25 inches (64 centimeters).

"These rains could result in significant lowlands floods," the forecasters said, adding that isolated tornadoes could occur along the central Gulf Coast region and parts of the lower Mississippi River Valley through the day.

"Even though Isaac is no longer a hurricane, life-threatening hazards from storm surge ... are still occurring," they said.

Isaac may wind up causing as much as US$2.5 billion in damage in and around Louisiana and in the offshore oil sector in the Gulf of Mexico, according to early estimates from natural disaster modeler Eqecat.

More than a half million people were left without power in Louisiana, and tens of thousands more huddled in darkened homes in Alabama, Florida and Mississippi after Isaac snapped utility poles and downed power lines.

In New Orleans, Mayor Mitch Landrieu has declared a dusk-to-dawn curfew after Isaac made landfall twice as a category one hurricane.

Across the state, more than 4,000 people were crammed into shelters.

Dozens of nursing home residents, many in wheelchairs, were among those taken to higher ground by the National Guard in high-water trucks.

U.S. President Barack Obama, who has been regularly briefed on the storm, late Wednesday declared a "major disaster" exists in Louisiana and Mississippi, paving the way for more federal aid to local authorities.

"We've got to make sure everybody's safe, then we'll start looking at what it'll take to recover," FEMA Administrator Craig Fugate said after surveying some of the damage on Wednesday.